What sort of diet helps people lose more weight?  Do overweight people lose more weight on a low-carbohydrate diet (like Atkins) or on a low-fat diet (like Weight Watchers and others)?

A carefully designed study published in the current issue of the Annals of Internal Medicine answers that question.  The study enrolled over 300 obese adults and randomized them to a low-carbohydrate diet or a low-fat diet.  Importantly, patients with diabetes, high cholesterol and high blood pressure were excluded.  The low-carbohydrate diet group was instructed to restrict carbohydrates and to have as much fats and proteins as needed to feel satisfied.  (This is essentially the Atkins diet.)  The group randomized to a low-fat diet was instructed to limit total calories to between 1200 and 1800 kcal per day, with less than 30% of total calories from fat.

Both groups attended periodic behavioral group sessions to discuss their progress and learn skills for persevering with the diet.  Both groups were also instructed to pursue an exercise program consisting largely of walking.  The groups were followed for two years.

The authors’ were trying to show that a low-carbohydrate diet would lead to greater weight loss, but actually the weight loss was the same in both groups.  Each group lost an average of 24 lb after one year and 15 lb (or an average of 7% of their body weight) after two years.  About a third of the participants in each group had dropped out by two years.

One lesson from this study is that perseverance in any diet program will yield meaningful weight loss.  It doesn’t matter which diet.  The second lesson, highlighted by the large numbers of drop-outs, is that this is hard to do.  So get started, and don’t quit.

Learn more:

Annals of Internal Medicine article:  Weight and Metabolic Outcomes After 2 Years on a Low-Carbohydrate Versus Low-Fat Diet

My post in 2009 comparing different diets:  Scientifically Proven Weight Loss Method: Eat Less

Obesity is an increasingly prevalent problem in developed countries, and a safe and effective medication for weight loss is eagerly sought.  Most weight loss medications have been plagued by serious side effects.

Fenfluramine, a medication used with phentermine in the popular “fen-phen” combination in the 1990s, was found to cause serious heart valve abnormalities and was withdrawn from the market.  The two prescription medications currently available are only modestly effective and each suffers from side effects that limit its use.  Sibutramine (Meridia) can elevate blood pressure and increase the risk of stroke and heart attack.  Orlistat (by prescription as Xenical, or over the counter as Alli) causes greasy stools and diarrhea.  These side effects make further weight gain seem like an appealing alternative.

A study in this week’s New England Journal of Medicine raises hopes for a new, safer weight loss medicine.  The study randomized over 3,000 overweight and obese patients to lorcaserin and to placebo for one year.  Importantly, all patients received ongoing counseling regarding diet and exercise.  Patients were instructed to engage in 30 minutes of moderate exercise daily and were taught to eat a diet containing 600 calories below their daily energy requirements.

At the end of the first year the group on lorcaserin lost an average of 13 lb, while the placebo group lost an average of 5 lb.  In the second year of the study, the patients on placebo for the first year continued receiving placebo.  The patients on lorcaserin during the first year were again randomized to receive lorcaserin or placebo the second year.  The patients who received lorcaserin the second year maintained the weight loss achieved during the first year, while the patients who received lorcaserin the first year and placebo the second year regained weight until their weight matched the group that was always on placebo.

Most tantalizing, however, was the safety profile.  Side effects were few, and tolerable.  Headache, dizziness and nausea were most common.  Since lorcaserin is in the same family as fenfluramine (though designed specifically to avoid the valvular side effect) the patients were monitored for valvular abnormalities.  The lorcaserin group did not develop valve problems any more frequently than in the placebo group.

The additional weight loss in the lorcaserin was not dramatic, suggesting that lorcaserin is no more effective (or maybe a little less effective) than sibutramine and orlistat.  But this preliminary study suggests that it is much safer than the existing alternatives.  If larger studies replicate this result, it may be a reasonable addition to diet and exercise.

Learn more:

New England Journal of Medicine article:  Multicenter, Placebo-Controlled Trial of Lorcaserin for Weight Management

New England Journal of Medicine editorial:  Drug Management of Obesity — Efficacy versus Safety

WebMD article:  Diet Drug Lorcaserin Safe, Effective, Study Finds

My regular readers know my skepticism about vitamin supplements.  I leap at the chance to bring you news that some vitamin has been tested for some disease and found useless.  So for balance, I have to also report when a well-designed study finds that a vitamin actually helps something.

This week’s New England Journal of medicine published a study about the treatment of nonalcoholic steatohepatitis (NASH).  NASH, also known informally as fatty liver, is a condition in which fat is deposited in the liver, causing liver inflammation.  It is more common in overweight patients, and those with diabetes and elevated triglycerides.  Fatty liver may eventually progress to liver failure.

Weight loss is the mainstay of treatment for fatty liver, and though some medications have been used for NASH, none have been proven to be effective.

The study randomized patients with fatty liver to placebo or 800 IU of vitamin E daily.  (There was a third group randomized to Actos, a diabetes medication, but that’s for another post.)  The patients were followed for about two years.  Improvement in their fatty liver was assessed by liver biopsy at the beginning and end of the study.

The patients taking vitamin E did quite a bit better than the patients taking placebo, with significantly more of the vitamin E patients having improvement or resolution of their fatty liver.  The authors of the study caution that the trial was too short to test the long-term safety of vitamin E, especially at this high dose.  They cite a worrisome study from 2005 that suggests that vitamin E at high doses may actually be associated with higher mortality.  (See second article, below.)

So if you have NASH talk to your doctor about starting vitamin E, and keep working on losing weight.  If you don’t have NASH and are taking vitamin E, consider donating your vitamin E to someone with NASH and taking a daily dose of nothing.

Learn more:

New England Journal of Medicine article: Pioglitazone, Vitamin E, or Placebo for Nonalcoholic Steatohepatitis

Annals of Internal Medicine Articles:  Meta-Analysis: High-Dosage Vitamin E Supplementation May Increase All-Cause Mortality

Two weeks ago I wrote a post about the mistake we make when we think of some medicine or food as generally “good for you” or “bad for you” as opposed to having specific benefits and harms.  I started with an anecdote in which a friend asked me whether diet sodas or regular sodas were better for you.

Susan Dopart, a terrific dietitian who I’ve known for over a decade, emailed me to bend my thinking about diet sodas and about non-nutritive sweeteners (i.e. artificial sweeteners) in general.  With her permission, I thought I’d share her thoughts with you.

She shared with me an article reviewing studies that link the use of artificial sweeteners with various adverse health outcomes, like obesity and insulin resistance.  The studies were all observational, that is, not randomized.  For example, one study showed that people who drink more diet sodas tend to weigh more than people who drink fewer diet sodas.  That’s exactly the kind of study that makes me want to pour lemon juice on my paper cuts.  The media misunderstands this kind of study and reports that diet sodas cause obesity.  But an equally likely possibility is that people who have stronger cravings for sweets will be overweight (by eating actual sweets) and will also drink more diet sodas (because they’re sweet).  It’s like noticing that my lawn wilts on the same days that the beaches are crowded and blaming the crowds for my wilting lawn.  But both are caused by a third phenomenon – hot days.

So, fancying myself the Defender of Science Against Confusing Nonsense, I emailed Susan that the studies were completely unconvincing and that artificial sweeteners haven’t been proven to have any adverse health effects.  Susan agreed that there is no solid science on the subject, but said that in the absence of good science the best guide we have is our professional experience.  She certainly has lots of experience, and she believes that sweeteners, whether natural or artificial, increase cravings for more sweets.  In her experience patients who have stopped drinking any kind of soda have noticed their cravings for sweets decrease.

That’s a potentially important lesson, and someone should test it rigorously.  In the meantime, I appreciate Susan sharing her expertise with us.

Learn more:

There is a mechanism that could explain how sweets cause increased cravings for sweets.  It’s a theory by psychologist Seth Roberts that weight gain is mediated by a learned association between tasty foods and calorie content.  This hasn’t been tested in a good study (yet) but I found his paper intriguing and easy to read.  (I have no idea what Susan Dopart thinks about it.)

What Makes Food Fattening?  A Pavlovian Theory of Weight Control by Seth Roberts

This week, a study in the Journal of the American Medical Association received a lot of undeserved media attention.  The study wanted to examine the relationship between exercise and long-term weight changes among women who were eating a normal diet (i.e. not dieting).  It followed for over a decade 34,000 women who were 45 years old or older and correlated their self-reported physical activity and body weight.

The study found that on average, the women gained about 6 lb during the study.  Among women who initially had normal weight (body mass index less than 25) there was a significant correlation between amount of exercise and maintenance of weight.  Women with initially normal weight who did at least 60 minutes a day of moderate to intense exercise maintained their weight, while those who did less tended to gain weight during the study.

The authors therefore concluded that for middle-aged women who are not dieting, 60 minutes of moderate exercise daily is necessary to prevent weight gain.  This conclusion was repeated in much of the media coverage (links below) trumpeting that women should be exercising much more than we previously thought necessary.

But hold on a minute!  First of all, the study is observational, not randomized.  If you really wanted to know the effect of different amounts of exercise on weight you would randomly assign women to different quantities of exercise, make sure they were doing the assigned amount, and follow their weight.  That’s not what happened here.  The women exercised as much or as little as they wanted, and that amount was correlated with their weight change.  But that means that anything that affects both exercise and weight could have skewed the results.  Women with chronic illnesses that cause weight gain (hypothyroidism, heart failure) would tend to feel too tired to exercise and also gain weight.  These women would tend to make the statistics look worse for sedentary women, though their weight gain had nothing to do with being sedentary.

Also, the amounts of exercise was self-reported, not observed by someone objective, making it possible that women with stable weights are simply more likely to exaggerate their reported exercise.  (Which reminds me, I have to take it easy this weekend after running 3 marathons and swimming up the Mississippi River this week.)

Finally, the correlation between exercise and weight gain was only found in women with normal weights.  In women who started with a BMI over 25, there was no connection found between how much they said they exercised and how much weight they gained.  Does that mean that overweight people shouldn’t exercise?  No.  It means that there’s nothing to learn from correlations and that we can only learn from a randomized experiment.

So this tells us nothing about how much women should be exercising to maintain their weight.  Perhaps it tells us that some conditions cause weight gain and inability to exercise.  Perhaps it tells us that thin women exaggerate when reporting their exercise habits.  Perhaps it tells us nothing.

So how can you tell how much exercise you need to maintain your weight?  Weigh yourself.  If you’re gaining weight, you should exercise more.

Learn more:

Journal of the American Medical Association article: Physical Activity and Weight Gain Prevention

Los Angeles Times article:  Women should exercise an hour a day to maintain weight, study says

Wall Street Journal article:  New Exercise Goal: 60 Minutes a Day

What’s my advice to my overweight patients?  Eat less and exercise more.  I give this advice every day, but following this advice is much harder than giving it.  Overweight people frequently struggle with diet and exercise for years, sometimes successfully, sometimes regaining their previously lost weight.

And as we become more overweight as a nation, obesity is no longer just a problem for adults.  Over 5 million adolescents are estimated to be obese in the US, which predicts bad things for their likelihood of developing diabetes, high blood pressure and other health problems.  Being an obese teen can also be a serious social and psychological burden.  Anyone who remembers adolescence knows that teens aren’t always accepting, nurturing and ethical peers.

I’ve written in the past about the slowly amassing scientific evidence that surgery for obesity has definite health advantages over continued attempts at diet and exercise.  This week, that evidence is extended to adolescents.

A study published in this issue of The Journal of the American Medical Association enrolled 50 teenagers between 14 and 18 years of age with a body mass index (BMI) higher than 35.  (For a person who is 5 feet 8 inches tall, a BMI of 35 means a weight of 235 lb.)  The enrolled teens also had to have been attempting to lose weight through diet and exercise for more than 3 years.

The teens were randomized to two groups.  One group underwent laparoscopic gastric banding.  In this surgery, an inflatable plastic belt is wrapped around the upper part of the stomach, decreasing how much food can be ingested.  In post-operative follow up the band can be adjusted by inflating or deflating it, thereby calibrating how much it constricts the stomach.  The second group was randomized to a supervised lifestyle intervention involving an individualized diet plan and a structured exercise program.  The groups were followed for two years.

The results were dramatic.  The group that underwent gastric banding lost an average of 76 lb over two years, compared to an average 7 lb in the lifestyle modification group.  The group that underwent gastric banding also had a higher quality of life and improvement in other health-related measurements.

The authors were quick to caution that gastric banding is no “quick fix”.  Patients still have to eat differently and be willing to have periodic follow up, potentially forever.  The authors still recommend diet and exercise as the first choice for weight loss.  But now for the many teens who do not lose weight after many attempts, there is a proven alternative.

Learn more:

Wall Street Journal article:  Weight-Loss Surgery for Obese Teens Backed by Study

Journal of the American Medical Association study:  Laparoscopic Adjustable Gastric Banding in Severely Obese Adolescents

Weight loss is one of the most common recommendations that doctors make.  How do we know if a patient should lose weight?  We usually use the Body Mass Index (BMI) which is a way to compare a patient’s weight to her height.  (For all you math geeks, it’s the weight in kilograms divided by the height in meters squared.  For all you physicists, I know the units make no sense.)  A BMI of 18.5 to 25 is considered normal.  A BMI of 25 to 30 is considered overweight, and over 30 is considered obese.  (See the link below to calculate your BMI.)

An article in the health section of Tuesday’s Wall Street Journal reminds us that BMI may not be telling us the whole story.  The article cites a study published in the European Heart Journal last year which followed over 6,000 adults with a normal BMI.  They all had their body fat percentage measured and were followed for about 9 years.

Surprisingly, even in these adults with a “normal” weight, those with a high body fat content had a higher likelihood of high blood pressure, high cholesterol and cardiovascular disease.

This study is too small to be definitive, and it’s observational, not randomized.  So we don’t know whether lowering body fat reverses any of these risk factors.  I’m not suggesting we all run out to measure our body fat content.  Still the article suggests a few tantalizing possibilities.

First, dieting may not be enough in improving cardiovascular health.  It may decrease overall weight without decreasing percent body fat.  Exercise is critical to burn fat and build muscle, thereby decreasing percent body fat.

Second, thin people who are inactive may have a high body fat percentage and may be falsely reassured by their “normal” weight.  This is what the authors call “normal weight obesity”.

Finally, for those of you who are exercising and not losing weight, don’t despair.  You may be losing inches from your waist, burning fat and building muscle, muscle while your weight stays the same.  Going by the weight alone is a recipe for frustration when in reality your health is improving.

Learn more:

The Centers for Disease Control BMI calculator

Wall Street Journal article:  The Scales Can Lie: Hidden Fat (only by subscription)

European Heart Journal article:  Normal weight obesity: a risk factor for cardiometabolic dysregulation and cardiovascular mortality

I’m grateful to all the readers of my weekly posts for all the stories you’ve pointed me to and all your valuable feedback.  Thanks for reading.

I’m grateful to my partners Dr. Rubencio Quintana and Dr. Dorothy Lowe for making our office a happy and intellectually stimulating place to work.

I’m grateful to Jaymes, Nancy and Jill for helping us take great care of our patients.  I couldn’t dream of a better support staff.

I’m grateful to my parents for bringing me to the US, where we are judged by our destinations, not by our origins.

I’m grateful to my wife for raising our kids, taking care of me, and working much harder than I do.

I’m grateful to my patients for letting me support my family by doing what I love (and in last year’s economy, I’m doubly grateful).

As is my tradition, I waive all of my patients’ dietary restrictions for 24 hours.  Count blessings, not calories.  Happy Thanksgiving!

Few things captivate the public more than a new diet.  From Atkins to Ornish to the Mediterranean diet, each new theory attracts attention and true-believer adherents and generates lots of book sales and interviews on daytime TV.  People passionately argue about whether a diet low in carbohydrates or low in fat is best for weight loss.  But until now no large trial has ever been done to answer the question.

This week’s New England Journal of Medicine published the largest study that directly compares different diets to measure which yields the greatest weight loss.  Over 800 overweight adults were randomized to one of four different diets.  (Importantly, diabetics were excluded.)  They were all given diets calculated to provide 750 calories fewer than they were burning daily, but the four diets differed in the percentage of calories from fat, protein, and carbohydrates.  Two of the diets were low-fat and two were high-fat.  Two were average-protein and two high-protein.  And the four diets provided a broad range of carbohydrate intake from low to high.

The participants were also asked to participate in periodic group counseling sessions and were instructed to do 90 minutes of moderate exercise per week.  They were followed for 2 years and their compliance with group attendance, diet and exercise was tracked.

Interestingly, the four diet groups lost weight at the same rate.  Six months into the study the participants lost an average of 13 lb, 7% of their body weight.  After that, on average, they slowly regained weight, so that by two years the average weight loss was 9 lb, the same in all four groups.

So diet and exercise lead to weight loss, and whichever low-calorie diet you can stick to is as good as any other.  So get started.  You can still buy the latest diet book and swear that it’s the best because your favorite actor lost weight on it.  Only you and I will know that you owe your success to the New England Journal of Medicine.

Learn more:

New England Journal of Medicine article:  Comparison of Weight-Loss Diets with Different Compositions of Fat, Protein, and Carbohydrates

NY Times article:  Study Zeroes In on Calories, Not Diet, for Loss

Many people use the occasion of the New Year to reflect on the last year and make specific goals for the next.  Resolutions can be very helpful motivators if they are specific, realistic and written down.  Just as people make goals for their careers and their relationships, resolutions for your health are a smart way to work for achievable targets in the health-related struggles you face.

So I encourage you this week to write down your health resolutions for 2009.  Obviously, what progress is achievable is as varied as the people making resolutions.  An elderly lady with balance problems may resolve to attend physical therapy and use her walker consistently and have an entire year without falling.  A younger more active woman may resolve to train for and compete in a triathlon.  There is no objective marker for your goals.  You just have to balance ambition with realism.

My suggestion is to make the resolutions as specific as possible.  Detailed planning will help overcome procrastination and a specific goal will keep you accountable.  So don’t write

• I’m going to exercise more
• I’m going to eat less
• I’m going to lose weight

but instead write something like

• I’m going to walk for 45 minutes Monday through Friday before work
• I’m going to join Weight Watchers and attend meetings weekly
• I’m going to weigh 205 lb on January 1, 2010

If you have diabetes, you should be following your glycated hemoglobin (or hemoglobin A1C).  Write down a goal for it.  If you’re struggling with your cholesterol, pick a goal for your LDL.  If your blood pressure is too high, write down something like

• My blood pressure will be lower than 140/90 on every doctor visit

If you’re smoking, 2009 is the perfect year to quit (on a specific date that you should pick now).  Obviously, some of these goals may require your physician’s help in terms of adjusting your medications, but your doctor can’t do it alone.

Making yourself accountable to others can also help keep you on track.  Give a copy of your resolutions to your spouse, to your doctor to attach to your chart, to anyone who knows you too well and cares for you too much to let you cheat yourself.

I wish us all a year of peace, health, prosperity and happiness.